Method and apparatus for maskless photolithography

ABSTRACT

A method and apparatus to create two dimensional and three dimensional structures using a maskless photolithography system that is semi-automated, directly reconfigurable, and does not require masks, templates or stencils to create each of the planes or layers on a multi layer two-dimensional or three dimensional structure. In an embodiment, the pattern generator comprises a micromirror array wherein the positioning of the mirrors in the micromirror array and the time duration of exposure can be modulated to produce gray scale patterns to photoform layers of continuously variable thickness. The desired pattern can be designed and stored using conventional computer aided drawing techniques and can be used to control the positioning of the individual mirrors in the micromirror array to reflect the corresponding desired pattern. A fixture for mounting of the substrate can be incorporated and can allow the substrate to be moved three dimensions. The fixture can be rotated in one, two, or three directions.

CROSS-REFERENCE TO A RELATED APPLICATION

The present application claims benefit of U.S. application Ser. No.11/398,905, filed Apr. 6, 2006, which is a divisional application ofU.S. application Ser. No. 10/408,696, filed Apr. 7, 2003, which is acontinuation-in-part of U.S. patent application Ser. No. 10/179,083,filed on Jun. 25, 2002, and a continuation-in-part of U.S. patentapplication Ser. No. 10/179,565, filed on Jun. 25, 2002, both of whichclaim priority to U.S. Provisional Application Ser. No. 60/301,218,filed Jun. 27, 2001, all of which are hereby incorporated by referenceherein in their entirety, including any figures, tables, or drawings.

The subject invention was made with government support under a researchproject supported by The Office of Naval Research funding referencenumber NOO014-98-1-0848. The government has certain rights in thisinvention.

BACKGROUND ART

Photolithography systems are known in the art that direct light beamsonto a photosensitive surface covered by a mask, etching a desiredpattern on the substrate corresponding to the void areas of the mask.Maskless photolithography systems are also known in the art as describedin Singh-Gasson, Sangeet et al., Nature Biotechnology 17, 974-78, 1999.The system described in this article uses an off-axis light sourcecoupled with a digital micromirror array to fabricate DNA chipscontaining probes for genes or other solid phase combinatorial chemistryto be performed in high-density microarrays.

A number of patents also exist which relate to maskless photolithographysystems, including U.S. Pat. Nos. 5,870,176; 6,060,224; 6,177,980; and6,251,550; all of which are incorporated herein by reference. While thepreviously described maskless photolithography systems address severalof the problems associated with mask based photolithography systems,such as distortion and uniformity of images, problems still arise.Notably, in environments requiring rapid prototyping and limitedproduction quantities, the advantages of maskless systems as a result ofefficiencies derived from quantities of scale are not realized. Further,prior art references lack the ability to provide rapid prototyping.

In particular, alignment of patterns with respect to target substratesin maskless systems can be problematic. Various solutions have beenproposed to mitigate the effect of alignment problems, including thedigital shifting of the projected mask pattern to compensate formisalignment of a substrate. However, this technique requires that thesubstrate be closely aligned initially and is better suited for highvolume production runs which incorporate automatic initial alignmentsystems. In a rapid prototyping, limited quantity environment, automatedmeans of initial alignment are not cost effective.

In addition, conventional maskless alignment systems are normallylimited to coplanar, two-dimensional alignment. However, there is a needin the art to create three-dimensional patterns on substrates. Creatingthree-dimensional patterns requires further alignment of the substratesin a third dimension perpendicular to the two coplanar dimensions. Inthe third dimension, computerized shifting of the mask pattern cannotcompensate for misalignments in a direction parallel with an incidentlight beam. As a result, an ability to align a substrate in a thirddimension in a rapid prototyping, reconfigurable environment is needed.

Another problem with maskless photolithography systems is that the maskpattern image projected is formed by pixels, instead of continuouslines. As a result, gaps may exist between adjacent pixels, which, whenprojected on a substrate, may allow the area between the pixels to beexposed, resulting in a break in the imaged pattern. For example, if thedesired pattern is a circuit, gaps may be inadvertently exposed andformed in a trace, resulting in an electrical gap. The exposure gapscaused by the pixel nature of the micromirror arrays, or pixelation, maycause open circuits or unwanted capacitive effects where trace width orthickness is critical.

Another problem with current art systems is the phenomenon of“stiction,” wherein the individual mirrors in a micromirror area tend to“stick” in a specific orientation if left in that position for anextended period. Consequently, a higher voltage needs to be applied tothe mirror drive to point the mirror in another desired direction. Thusthe micromirror array consumes more power than normal and affects thereliability of the mirror.

It is known in the art to use gray scale masks in photolithography toform continuously variable material profiles on substrates, such asmicrolens arrays (wherein each lens can have a different profile),refractive and diffractive micro-optics, precision tapered structures,sinusoidal transmittance gratings, arbitrary shaped micro-optics, andother 3D microstructures, including optical micro-electromechanicaldevices (MEMS). One type of gray scale mask is a halftone chrome maskthat consists, for example, of mixtures of 0.5 micron×0.5 micron chromespots which are totally opaque and 0.5 micron×0.5 micron clear spotswhich are totally transparent due to the absence of chrome film coatingon the glass photomask substrate. The transmittance of a gray scaleresolution element in a halftone chrome mask is determined by the ratioof the number of chrome spots to clear spots. Transmittance decreases asthe ratio of chrome spots to clear spots is increased. For a gray scalechrome mask capable of 16 gray levels, a gray scale resolution elementmust consist of 16 binary spots. A binary spot of the chrome mask iseither a chrome spot or a clear spot. When all 16 binary spots in a grayscale resolution element are chrome spots, the gray scale resolutionelement is totally opaque. However, the images produced using thismethod are halftone images, not true gray scale images.

Gray scale masks have also been implemented in a photo-emulsion film ora photographic emulsion glass plate and are halftone gray scalepatterns, since each silver grain in a developed photographic emulsionis totally opaque. The gray scale is produced by varying the numberdensity of the silver grains. The spacing between the grains aretransparent. The size of silver grains is not uniform and may rangefrom, for example, about 0.1 micron to about 1 micron in ahigh-resolution photoemulsion plate. Therefore, it is difficult toobtain consistent imaging results because of the nonuniformity of grainsize.

Yet another type of gray scale is the High Energy Beam Sensitive (HEBS)glass, manufactured, for example by Canyon Material, Inc. In the HEBSglass, process glass photomasks having varying transmissive propertiesare created in photosensitive glass according to the energy density of ahigh energy beam impinging on the glass surface. The resulting varyingtransmissibility glass substrate is used as a gray scale photomask instandard photolithographic processes to create micro-optical elementssuch as refractive micro lens arrays, diffractive optical elements,prism couples, and three-dimensional microstructures.

Although the HEBS glass process allows true gray scale imaging, aphotomask must still be used for photolithographic processing ofsubstrates. While effective, the use of physical masks inphotolithography has numerous drawbacks, including the cost offabricating masks, the time required to produce the sets of masks neededto fabricate semiconductors, the diffraction effects resulting fromlight from a light source being diffracted from opaque portions of themask, registration errors during mask alignment for multilevel patterns,color centers formed in the mask substrate, defects in the mask, thenecessity for periodic cleaning and the deterioration of the mask as aconsequence of continuous cleaning.

It also known in the art to use maskless gray scale x-ray lithography.Maskless gray-scale x-ray lithography has been disclosed (Frank Hartley,Maskless Gray-Scale X-ray Lithography, NASA Tech Brief # NPO-20445,July, 2000). In this reference, a photoresist coated substrate to bepatterned is exposed to a parallel beam of hard x-rays. The photoresistis translated across the beam at a varying rate to effectone-dimensional spatial variations in the radiation dose received by thephotoresist. The radiation dose delivered to the photoresist on asubstrate is made to vary spatially, within a range in which thesolubility of the exposed photoresist in a developer liquid varies withthe dose.

In conventional gray-scale x-ray lithography, the required spatialvariation in the dose is achieved by use of a mask. The mask and thephotoresist-covered substrate are translated as a unit across an x-raybeam at a constant rate to obtain the required integrated dose to themask. In the disclosed maskless technique, the photoresist is notmasked. The gradients in the radiation dose needed to obtain gradientsin the density of the developed photoresist are generated by controlledvariations in the rate of translation of the x-ray beam across thephotoresist. These controlled variations define the desired features(variations of the height of the subsequently developed photoresist) towithin sub-micron dimensions, depending on the exposure time of thesubstrate.

After exposure to x-rays, the photoresist coated substrate is developedin the customary manner. After development, the photoresist is dried,giving rise to spatial consolidation of the photoresist into thicknessgradients corresponding to the density gradients. The dosage gradientsare chosen to achieve desired final thickness gradients, for example, toproduce triangular- or saw tooth-cross-section blazes for diffractiongratings. However, the x-rays are inherently dangerous and their use ishighly regulated, requiring sophisticated equipment to generate anddirect the radiation. In addition, the disclosed techniques requirecomplex translational stages to expose and generate patterns onsubstrates.

In addition, it is also known in the art to use lasers to createpatterns on large photoresist coated substrates. In particular, asdisclosed in R. Bawn, et al., “Micromachining System Accommodates LargeWafers,” Laser Focus World, January 2001, pp. 189-192, and “LaserMicrofabrication Process,” Proceedings of ICALEO 2000, Paper A49,October 2000, laser lithography techniques can be used to createpatterns on large substrates. In the disclosed systems,laser-micromachining systems for large area patterning require a lasersource, optics for conditioning and focusing the beam, and a way toprecisely control and point the beam. Patterns are produced onsubstrates by precisely positioning and focusing the laser beam oversmall area and ablating away the substrate material to form a desiredpattern. The laser is then repositioned and another area of thesubstrate is ablated. The process is continued until the desired patternon a substrate has been created. In this manner a large substrate can besequential processed to create large patterned substrates. However, onlysmall areas can be written at one time because of the small beamwidth ofthe laser, making large area patterning prohibitively time consuming.

Accordingly, there is a need in the art for a method and system formaskless photolithography to provide a more effective way to fabricatecustom devices in a low volume production environment. This system needsto combine ease of use, reconfigurability, and the ability to providecoarse manual alignment and automated fine alignment of mask patterns.In addition the system needs to address the exposure gaps inherent inthe process due to the pixel nature of the projected mask and providemeans for eliminating stiction. In summary, the system needs to provideall the advantages of a maskless photolithography system at a reasonablecost, and include capabilities tailored to direct writing in a rapidprototyping environment.

In addition, there is a need in the art for a method and system formaskless photolithography to provide gray scale capability and largearea patterning of substrates. This system can combine ease of use,reconfigurability, and the ability to provide gray scale patterns tocreate variable thickness on exposed substrates. In addition the systemcan allow patterning large areas in a single exposure. The system canprovide many of the advantages of a maskless photolithography system ata reasonable cost, and include capabilities tailored to gray scaleimaging and large area pattern generation in a cost effective, easy toimplement system.

SUMMARY OF THE INVENTION

In view of the foregoing deficiencies of the prior art, it is an objectof the present invention to provide a maskless photolithography systemfor creating 2-D and 3-D patterns on substrates.

It is another object of the present invention to provide an easy to use,reconfigurable, rapid prototyping maskless photolithography system.

It is still another object of the present invention to provide adirectly coupled optical system for maskless photolithography thatensures efficient transfer of light energy to a substrate for performingphotolithography.

It is yet another object of the present invention to provide a projectedimage for maskless photolithography that is free from distortion anduniform throughout the exposure area.

It is still another object of the present invention to provide apositioning fixture, selectively movable in three dimensions toaccurately position a substrate for maskless photolithography.

It is another object of the present invention to provide a masklessphotolithography for creating micro and macro three-dimensionalstructures.

It is another object of the present invention to provide gray scalepatterning using a maskless photolithography system.

To achieve these objects, a system and method are provided to create twodimensional and three dimensional structures using a masklessphotolithography system that is directly reconfigurable and does notrequire masks, templates or stencils to create each of the planes orlayers on a multi layer two-dimensional or three dimensional structure.In an embodiment, the invention uses a micromirror array comprising upto several million elements to modulate light onto a substrate that hasphotoreactive compounds applied to the exposed surface. The desiredpattern is designed and stored using conventional computer aided drawingtechniques and is used to control the positioning of the individualmirrors in the micromirror array to reflect the corresponding desiredpattern. Light impinging on the array is reflected to or directed awayfrom the substrate to create light and dark spots on the substrateaccording to the pattern. In addition, an alignment fixture, movable inthree dimensions, for mounting of the substrate is provided. Thealignment fixture allows the affixed substrate to be moved in threedimensions, providing alignment in two, coplanar dimensions and a thirddimension perpendicular to the two coplanar dimensions. By providingalignment in the third dimensional direction, the inventionadvantageously provides the capability to produce three-dimensionalstructures on a substrate. Further, the positioning information providedto the micromirror array can be modulated to cause the individualmirrors to change their angular position during exposure to reduce theeffects of pixelation and stiction and/or produce gray scale patterns.Further, the subject invention can be used to produce large scalepatterning on, for example, substrates.

The advantages of the invention are numerous. One significant advantageis the ability to use the invention as a reconfigurable, rapidprototyping tool for creating two-dimensional and three dimensionalmicro and macroscopic objects. Another advantage of the invention isthat it provides the ability to reduce prototyping costs and enabledevices to be fabricated more quickly with less risk. Yet anotheradvantage of the invention is the ability to utilize different designsand operating conditions on a single device. A further advantage is theability to use computer network to transfer designs across networks forimmediate light exposure of a substrate. Still another advantage of thecurrent invention is a reduction in cost for prototyping activitiesrealized by the elimination of physical masks and the ability to createboth positive and negative tone images using the same array. Yet anotheradvantage of the current invention is that pattern generation can beperformed optically without having to use expensive vacuum systemrequired by conventional mask-based photolithography. A particularadvantage of the current invention is the ability to createthree-dimensional devices using an alignment stage to selectively exposesuccessive layers in a substrate. By modulating the movement of themicromirror arrays, the negative effects of pixelation and stiction ofmicromirrors is reduced.

The subject invention can allow the ability to photoform continuouslyvariable pattern thickness on substrates by using the disclosed grayscale lithographic techniques that do not have a gray scale mask as anelement in the gray scale lithographic system. Another advantage of theinvention is the ability to efficiently create patterns on larger areasthan conventionally possible.

By providing the ability to individually control the individualmicromirrors of the mirror array, any arbitrary micro or macroscopicstructure can easily and quickly be created in substrates such aspolymers, metals, or ceramics. Patterns such as glasses, microfluidicnetworks, thin film devices, hybrid material devices, microelectromechanical machines (MEMs), photomasks and combinations of theabove mentioned devices can be created using the reconfigurable,application specific photolithography system disclosed.

All patents, patent applications, provisional applications, andpublications referred to or cited herein, or from which a claim forbenefit of priority has been made, are incorporated herein by referencein their entirety to the extent they are not inconsistent with theexplicit teachings of this specification.

Other aspects and advantages of the invention will become apparent fromthe following detailed description taken in conjunction with theaccompanying drawings, illustrating, by way of example, the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above recited and other advantagesand objects of the invention are obtained, a more particular descriptionof the invention briefly described above will be rendered by referenceto specific embodiments thereof, which are illustrated in the appendeddrawings. Understanding that these drawings depict only typicalembodiments of the invention and are not therefore to be considered tobe limiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1A illustrates a maskless photolithography system according to anembodiment of the present invention.

FIG. 1B illustrates a maskless photolithography system using a plasmadisplay device according to an embodiment of the present invention.

FIG. 2A illustrates a gray scale maskless photolithography system usinga micromirror array according to an embodiment of the present invention.

FIG. 2B illustrates a gray scale maskless photolithography system usinga variably transmissive light filter device according to an embodimentof the present invention.

FIG. 3 is a flow chart illustrating a gray scale masklessphotolithography method according to an embodiment of the presentinvention.

FIG. 4 is a flow chart illustrating a large area patterning masklessphotolithography method according to an embodiment of the presentinvention.

FIG. 5 is a flow chart illustrating a maskless photolithography methodaccording to an embodiment of the present invention.

FIG. 6 is a graph showing the relation between exposure area and minimumfeature size according to the current invention.

FIG. 7 is a graph showing an exemplary spectral output of the currentinvention.

It should be understood that in certain situations for reasons ofcomputational efficiency or ease of maintenance, the ordering andrelationships of the blocks of the illustrated flow charts could berearranged or re-associated by one skilled in the art. While the presentinvention will be described with reference to the details of theembodiments of the invention shown in the drawings, these details arenot intended to limit the scope of the invention.

DETAILED DISCLOSURE OF THE INVENTION

References will now be made in detail to the embodiments consistent withthe invention, examples of which are illustrated in the accompanyingdrawings. First, briefly, the invention is a system and method to createtwo dimensional and three dimensional structures using a masklessphotolithography system comprising a maskless pattern generator that isdirectly reconfigurable and does not require masks, templates orstencils to create each of the planes or layers on a multi layertwo-dimensional or three dimensional structure. In an embodiment, theinvention uses a micromirror array comprising up to several millionelements to modulate light onto a substrate that has photoreactive orphotoresist compounds applied to the exposed surface. The desiredpattern is designed and stored using conventional computer aided drawingtechniques and is used to control the positioning of the individualmirrors in the micromirror array to reflect the corresponding desiredpattern. Light impinging on the array is reflected to or directed awayfrom the substrate to create light and dark spots on the substrateaccording to the desired pattern. In addition, an alignment fixture formounting of the substrate allows the substrate to be moved in threedimensions, providing alignment in two, coplanar dimensions and thecapability to produce three dimensional structures by aligning thesubstrate in a third dimension perpendicular to the two coplanardimensions.

The subject invention can provide a system and method for photoformingphotosensitive materials using maskless, gray scale photolithographysystem. In addition, the invention provides a directly coupled opticalsystem for large area patterning using a maskless photolithographysystem.

In a specific embodiment, the alignment fixture for mounting of thesubstrate can incorporate a means for positioning the aligned fixtureand, therefore, the substrate, in one, two, or three dimensions. In aspecific embodiment, the means for positioning the alignment fixture canbe interconnected with the system for controlling the positioning of theindividual mirrors in the micromirror array, such that the system canalso control the movement of the substrate in one, two, or threedimensions. This can allow the system to coordinate the control of theposition of micromirrors and control of the position of the substrate toaccomplish the desired mask pattern. In a further specific embodiment,the alignment fixture can incorporate a means for allowing rotation ofthe substrate in one, two, or three directions. The means for allowingrotation of the substrate can be interconnected with the system forcontrolling the positioning of the individual mirrors in the micromirrorarray, such that the system can also control the rotation of thesubstrate in one, two, or three directions. This can allow the system tocoordinate the control of the position of the micromirrors and therotation of the substrate to accomplish the desired mask pattern. Thesystem can also be allowed to coordinate the control of the position ofthe micromirrors, the movement of the substrate, in one, two, or threedimensions, and the rotation of the substrate in one, two, or threedirections to accomplish the desired mask pattern. In another specificembodiment, movement of the micromirror array 14 in one, two, or threedimensions and/or rotation of micromirror array 14 in one, two, or threedirections can be accomplished. Such movement and/or rotation ofmicromirror array 14 can be accomplished by interconnected computersystem 16 with the means to accomplish the movement and/or rotation.Accordingly, the computer system can coordinate the movement and/orrotation of the substrate and the movement and/or rotation ofmicromirror array 14 to accomplish the desired mask pattern.

I. Maskless Photolithography System

Referring now to FIG. 1A, an embodiment of the current inventionincludes a light source 10, a removable filter 11, a first lens system12, a micromirror array 14, a computer system 16, a second lens system18, a substrate 20, mounted on a movable alignment fixture 22, and anoptical viewer 24. A layer of photoreactive chemicals 21 is disposed onthe substrate 20. It should be understood that the invention is notlimited to the use of a substrate 20 having a layer of photoreactivechemicals 21. Any photoreactive material, such as a photoreactivesubstrate, may be used in conjunction with the invention to photoformobjects by patterned light exposure.

As shown, light source 10 provides a beam of collimated light, or lightbeam 26, which can be selectively filtered by inserting or removingfilter 11 from light beam 26. Light beam 26 is projected upon first lenssystem 12 and then onto micromirror array 14, wherein each mirror in themicromirror array corresponds to a pixel of the mask pattern.Micromirror array 14 is controlled by computer system 16 over signalline(s) 15 to reflect light according to a desired mask pattern storedin memory. In addition, computer system 16 can shift the desired maskpattern in two dimensions to align the pattern with the substrate 20mounted on movable alignment fixture 22. Precise pattern alignments areoptionally made electronically by shifting the mask pattern informationprovided to the micromirror array such that the image, or pattern,reflected to the substrate is translated to correct for misalignment.For example, if the mask pattern needs to be shifted to the right onepixel width to be properly aligned on the substrate, the computercompensates for the misalignment by shifting the mask pattern one pixelwidth to the right.

In an embodiment, micromirror array 14 is controlled to modulate thepositioning of the mirror to prevent stiction and pixelation. Theindividual mirrors of micromirror array 14 are driven to vary theirangular orientation with respect to on-axis illumination during exposureof a substrate. The light beam 26 incident on the micromirror array isreflected as a patterned light beam 27 by reflecting or orienting thedesired pixels toward the substrate 20, and reflecting or orienting theundesired pixels away from the substrate 20. After being reflected in adesired pattern from micromirror array 14, patterned light beam 27passes through second lens system 18, and impinges on a layer ofphotoreactive chemicals 21 applied to substrate 20, thereby creating apattern on substrate 20 by producing a reaction between the layer ofphotoreactive chemicals 21 and substrate 20 and/or producing aphoto-reaction in the layer of photoreactive chemicals on the substrate20. Alternatively, a photoresist chemical could be applied to substrate20 to etch areas of substrate 20 not masked off by the mask patternduring an exposure.

The mask pattern described above is a programmable mask patterngenerated with the use of computer aided design and is resident oncomputer system 16. Accordingly, the mask pattern to be transferred tothe layer of photoreactive chemicals 21 and substrate 20 is aselectively programmable mask pattern. Thus, with a programmable maskpattern, any portion of the pattern on the substrate 20 can bemanipulated and/or changed as desired for rendering of desired changesas may be needed, furthermore, on a significantly reduced cycle time.

Micromirror array 14 described above is a micro mirror device known inthe art. With the micro mirror device, light is reflected according to apattern of pixels as controlled according to a prescribed pixel/bit maskpattern received from computer system 16. The light reflecting from themicro mirror device thus contains the desired mask pattern information.A micro mirror device may include any suitable light valve, for example,such as that used in projection television systems and which arecommercially available. Light valves are also referred to as deformablemirror devices or digital mirror devices (DMD). One example of a DMD isillustrated in U.S. Pat. No. 5,079,544 and patents referenced therein,in which the light valve consists of an array of tiny movablemirror-like pixels for deflecting a beam of light either to a displayscreen (ON) or away from the display optics (OFF). The pixels of thelight valve device are also capable of being switched very rapidly.Thus, with the use of the light valve, the photolithography system ofthe present disclosure can implement changes in the mask pattern in arelatively quick manner. The light valve is used to modulate light inaccordance with mask pattern information provided by the computer system16. In addition, the DMD reflects light, thus no appreciable loss inintensity occurs when the patterned light is projected upon the desiredsubject during the lithographic mask exposure.

In an embodiment, the positioning of the mirrors in the micromirrorarray and the time duration of exposure can be modulated whilepositioned in a desired mask pattern. By dynamically changing theposition of the mirrors while exposing a substrate and the time durationof exposure, the effects of pixelation on the exposed substrate andstiction of the mirrors can be reduced and/or gray scaled patterns canbe produced, wherein the depth of photoreaction can be variablycontrolled to photoform layers of continuously variable thickness and/orcomposition. The duty cycle of the modulation command can be selectivelymodified to achieve an optimum ratio between on axis, direct exposure,and off axis, indirect exposure. The depth of photoactivation in thephoto reactive material can be proportional to the time length andintensity of exposure. As a result, the micromirrors are constantlymoving to prevent stiction, and further allow integration of interpixelexposure areas around directly radiated pixels to provide uniformcoverage of the mask pattern to eliminate pixelation. In addition,pixelation can be reduced by defocusing the lens to “blend” adjacentpixels.

Typically, the micromirrors are quadrilateral in shape and mounted in anarray such that they can be individually driven to deflect along adiagonal axis, for a maximum deflection of about 10 degrees away fromnormal in either direction along the diagonal axis. Light is typicallyreflected to a target by driving the mirror 10 degrees form normal inone direction to expose a target (“on”), and driven 10 degrees fromnormal in the opposite direction to reflect light away form the target(“off”). Variations in light intensity projected on a target can beaccomplished by binary pulse width modulation of the driving signal. Thelength of duration at a particular on or off state is governed by thebinary code representing various durations of time for light to be on oroff.

Advantageously, the present system can allow an image to be shiftedelectronically to provide fine alignment of the pattern on substrate 20.The mask pattern is digitally shifted according to alignment informationin one or more directions for achieving a desired mask alignment onsubstrate 20. Adjustments in alignment are carried out electronically inthe mask bit pattern information provided to the light valve. As aresult, fine adjustments in pattern alignment can thus be easilyaccomplished.

Movable alignment fixture 22, in conjunction with optical viewer 24,provides the capability to initially align substrate 20 under light beam26 using mechanical alignment mechanisms (not shown) to align substrate20 in three dimensions. Optical viewer 24 can incorporate, for example,cameras and/or other vision systems. The mechanical alignment system mayinclude gears, pulleys, belts, chains, rods, screws, hydraulics,pneumatics, piezo motion or combinations thereof as known in the art tosupport and move an object in three dimensions. While performingalignment procedures, filter 11 is inserted in light beam 26 to filterout the wavelengths of light that react with the layer of photoreactivechemicals 21 on substrate 20. Optical viewer 24 can provide a means tomonitor the positioning of substrate during manual alignment. Whileproviding alignment in coplanar first and second dimensions, alignmentfixture 22 advantageously provides alignment in a directionperpendicular to the coplanar first and second dimensions, allowingfabrication of three dimensional objects. For example, to gain morecontrol over sidewall profiles or to produce complicated structures,multiple layers of substrate 20 can be sequentially exposed by aligningsubstrate 20 in the third dimension to create three-dimensionalfeatures. Coupled with computer controlled alignment of the desiredpattern, the invention provides the capability to quickly manually alignsubstrate 20 under light beam 26 and allows computer system 16 toautomatically finely tune the alignment before exposing layer ofphotoreactive chemicals 21 on substrate 20. Moveable alignment fixture22 can incorporate a means to allow rotation of the substrate in one,two, or three directions. In a specific embodiment, the alignmentfixture can be interconnected with computer system 16 so as to allowcomputer system 16 to coordinate the control of the position of themicromirrors and the rotation of the substrate in one, two, or threedirections and/or the movement of the substrate in one, two, or threedimensions, to accomplish the desired mask pattern.

In an alternative embodiment shown in FIG. 1B, a plasma display device13 can be substituted for the micromirror array 14, light source 10 andassociated optics of FIG. 1A. Referring now to FIG. 1B, an embodiment ofthe current invention includes a plasma display device 13, a computersystem 12, a lens system 16, a substrate 20, mounted on a movablealignment fixture 22, and an optical viewer 24. A layer of photoreactivechemicals 21 is disposed on the substrate 20.

As shown, plasma display device 13 generates a beam of light, orpatterned light beam 27, wherein each pixel of the plasma display 13corresponds to a pixel of the mask pattern. Plasma display device 13 iscontrolled by computer system 16 over signal line(s) 14 to generatelight according to a desired mask pattern stored in memory. In addition,computer system 12 can optionally shift the desired mask pattern in twodimensions to align the pattern with the substrate 20 mounted on movablealignment fixture 22. Precise pattern alignments are made electronicallyby shifting the mask pattern information provided to the plasma displaydevice 13 such that the image directed to the substrate is translated tocorrect for misalignment. For example, if the mask pattern needs to beshifted to the right one pixel width to be properly aligned on thesubstrate, the computer compensates for the misalignment by shifting themask pattern one pixel width to the right.

The patterned light beam radiated from plasma display device 13 can beselectively filtered by inserting or removing filter 18 from patternedlight beam 27. Filtering can take place at any point along the lightbeam path to prevent exposure during alignment. A lens system 16 cancollimate and condition the light beam as desired. After passing throughlens system 16, patterned light beam 27 impinges on a layer ofphotoreactive chemicals 21 applied to substrate 20, thereby creating apattern on substrate 20 by producing a photo-reaction in the, layer ofphotoreactive chemicals 21 on the substrate 20. Alternatively, aphotoresist chemical could be applied to substrate 20 to etch areas ofsubstrate 20 not masked off by the mask pattern during an exposure. In aspecific embodiment, the plasma cell can be variably excited to createvariable luminosity.

The system provides optics, a light source, and integrated electroniccomponents used to directly generate patterns for the exposure ofphotoresist and other photoimagable materials. A broad band spectrum,high intensity white light source provides the exposure energy for theprocess. This light is then filtered and optimized for the exposureprocess, using a variety of integrated optical components. A directcoupled optical delivery system ensures efficient transfer of the lightenergy. Using proven optical techniques, the projected image is free ofdistortion and uniform through out the exposure area. With the optimizedoptical stream, the image is imposed in the light path, providing thefinal exposure pattern. This pattern is then transferred to thesubstrate surface and used to expose the photo-sensitive materialrequired in the user's fabrication process.

A personal computer operably connected to a micromirror array providesmask patterns. The mask patterns are generated in the computer and thentransferred to the micromirror array to provide the optical pattern forexposure. The pattern is transferred to a substrate and is observedusing an optical microscope. This microscope is needed for patternalignment to the substrate. Alignment is controlled through the use of acourse alignment stage provided by a mechanically movable substratemounting alignment fixture, combined with a fine, electronic alignmentstage. This fine alignment stage is computer controlled and aligns themask pattern reflected from the micromirror instead of moving thealignment fixture, thereby offering exceptional accuracy andrepeatability. Once alignment is complete, substrate exposure occurs.Through the use of a step and repeat method, the entire substratesurface can be exposed and multiple layers can be created using analignment stage movable in a direction parallel to the light beam.

In addition, according the invention, three-dimensional patterns can becreated using the three dimension alignment capabilities disclosedabove. For example, patterning using thick photo resist or multilayerpatterning of individual photoresist layers. These techniques can beused to provide either a photomask for subsequent etching of substratematerials or if the photopolymer is compatible with the chemistry usedin the device, the fabricated features can be used as part of the deviceitself.

The system described above can be adapted for use in novel environments.Specifically, a system and method of maskless photolithography can beused to create 2-D and 3-D patterns of continuously variable thicknesson objects using gray scale photolithography. In addition, the systemcan be used to provide rapid, large area patterning of photoreactivematerials.

II. Gray Scale Maskless Photolithography

A. System for Gray Scale Maskless Photolithography

Referring now to FIG. 2A, an embodiment of the current invention forgray scale photolithography will now be described. In the embodiment, amaskless photolithography system, as described above, is combined withgray scale controller to photoform continuously variable thickness inphotoreactive materials. Patterns generated on the photoreactivematerial are defined by the patterned light radiated by the masklessphotolithography system, where areas of continuously variable thicknessand/or composition are created by varying the intensity or time durationof the patterned light exposure. By using photoreactive materialswherein the thickness of the final deposit and/or composition is afunction of exposure time or intensity, a variety of 2D and 3Dheterogenous microstructures and designs of multilayer, continuouslyvarying thickness and/or composition can be created.

As shown in FIG. 2A, a maskless lithography system for gray scalepatterning includes a light source 10, a removable filter 11, a firstlens system 12, a micromirror array 14, a computer system 16, a grayscale controller 17, a second lens system 18, and a substrate 20, coatedwith a layer of photoreactive chemicals 21. In alternative embodiments,a movable alignment fixture 22 upon which the substrate 20 is mounted,and an optical viewer 24 are provided as depicted in FIG. 1A.

As depicted in FIG. 2A, light source 10 provides a beam of collimatedlight, or light beam 26, which can be selectively filtered by insertingor removing filter 11 from light beam 26. Light beam 26 is projectedupon first lens system 12 and then onto micromirror array 14, whereineach mirror in the micromirror array corresponds to a pixel of the maskpattern. Computer system 20 provides, over signal line(s) 15, maskpatterns to a gray scale controller 17, which modulates the receivedmask patterns to provide a gray scale mask pattern to the micromirrorarray 14. Micromirror then reflects light according to the gray scalemask pattern. In addition, computer system 16 can optionally shift thedesired mask pattern in two dimensions to align the pattern with thesubstrate 20.

In another embodiment, as shown on FIG. 2B, a variably transmissivefilter array device 9, such as a transmissive LCD display, is used toprovide gray scaling. The variably transmissive filter array device 9has individually addressable pixels, capable of being addressed to beopaque, to prevent light transmission, and capable of being addressed tobe transparent, to allow light transmission.

As shown in FIG. 2B, the maskless lithography system for gray scalepatterning includes a light source 10, a removable filter 11, a firstlens system 12, a variably transmissive filter array device 9, acomputer system 16, a gray scale controller 17, a second lens system 18,and a substrate 20, coated with a layer of photoreactive chemicals 21.In alternative embodiments, a movable alignment fixture 22 upon whichthe substrate 20 is mounted, and an optical viewer 24 are provided asdepicted in FIG. 1A.

As depicted in FIG. 2B, light source 10 provides a beam of collimatedlight, or light beam 26, which can be selectively filtered by insertingor removing filter 11 from light beam 26. Light beam 26 is projectedupon first lens system 12 and then onto the variably transmissive filterarray device 9, wherein each individually addressable pixel of thevariably transmissive filter array device 9 can be signaled to be opaqueor transparent. Computer system 16 provides, over signal line(s) 15,mask patterns to a gray scale controller 17, which modulates thereceived mask patterns to provide a gray scale mask pattern to thevariably transmissive filter array device 9. The variably transmissivefilter array device 9 then transmits, by driving the addressed pixel toa transparent state, or blocks light, by driving the addressed to anopaque state, according to the gray scale mask pattern. In addition,computer system 16 can optionally shift the desired mask pattern in twodimensions to align the pattern with the substrate 20.

B. Method for Gray Scale Maskless Photolithography

As depicted in FIG. 3 a method of using the current invention tophotoform photosensitive materials using gray scale lithography will nowbe described. It should be understood that in certain situations forreasons of computational efficiency or ease of maintenance, the orderingand relationships of the blocks of the illustrated flow charts could berearranged or re-associated by one skilled in the art. Starting fromstep 50, a desired mask pattern is designed and stored on computersystem 16 in step 52. Alternatively, mask patterns can be designed onother computer systems and imported into computer system 16. Next, instep 54, a photosensitive material is provided for exposure to thepatterned light beam 27. For example, the substrate 20 is affixed toalignment fixture 22 and coated with a layer of photoreactive chemicals21 for exposure to the patterned light beam 27. After the photosensitivematerial is provided for exposure, the filter 11 is placed in the lightbeam 26 path according to step 56 to filter the light and preventexposure of the photosensitive material until the system has beenaligned.

Next, the computer system 16 is instructed to provide the resident maskpattern information to micromirror array 14 via the gray scalecontroller 17, as shown in step 58, and the micromirror array 14responds by orienting each individual mirror to reflect or direct lightbeam 26 away from the photosensitive material according to the desiredpattern. In an alternative embodiment, a variably transmissive filterarray device 9 is used and the projected light beam 26 is directedthrough the variably transmissive filter array device 9 and towards thesubstrate 20. The variably transmissive filter array device 9 respondsto the resident mask pattern information by preventing lighttransmission by causing the individual pixels of the variablytransmissive filter array device 9 to be in an opaque state or atransparent state according to said gray scale mask patterns provided bysaid gray scale mask pattern controller 17. Consequently, the intensityof said gray scaled patterned light transmitted to the photosensitivematerial is varied by modulating the transmissive properties of saidvariably transmissive filter array device to achieve gray scalephotosculpting and/or photo transforming of the photosensitive material.

Next, alignment of the photosensitive material is enabled by excitingthe light source 10 to provide a light beam in step 60, projecting lightbeam 26 through first lens system 12, and then onto micromirror array14. In turn, micromirror array 14 reflects light beam 26 through secondlens system 18 and the photosensitive material.

With the desired pattern projected on the photosensitive material, thematerial can be manually and/or automatically aligned in threedimensions according to step 62, for example, by moving alignmentfixture 22 to ensure that the photosensitive material is properlylocated in light beam 26. Proper alignment can be verified by viewingthe projected pattern on the photosensitive material through opticalviewer 24. In an optional embodiment, once the photosensitive materialis manually and/or automatically aligned, alignment information can beprovided to computer system 16 and computer system 16 automaticallyadjusts the micromirror 14 by shifting the pattern in two dimensions toattain proper alignment in step 64. Having aligned the photosensitivematerial, the material is exposed in step 68 by removing filter 11 fromlight beam 26 in step 68 and allowing the light to cause a photoreactionin the photosensitive material for a required reaction time depending onthe photoreactive chemicals used. For example, using standard Novolac™positive photoresist an exposure time of 60 seconds is used.

To accomplish gray scale patterning, the gray scale controller 17modulates the mask pattern information in step 70 provided to themicromirror 14 to achieve a desired gray scale pattern 70. In anembodiment, the angular position and time duration of the angularpositioning of the mirrors in micromirror array 14 is varied accordingto commands from gray scale controller 17 to create areas of varyingthickness in the photosensitive material, and/or composition, accordingto the time duration and intensity of direct exposure. For example, whenmasking a 25 micron square feature on a photoresist coated substrate,angular position and time duration of the angular positioning of themirrors in micromirror array 14 might be varied by the gray scalecontroller 17 so that the mask effectively covers an area of 36 micronssquare, centered on the desired 25 micron square feature. By varying thetime of exposure around the perimeter of the 25 micron square feature,the resulting feature has sides that gradually slope away from thedirectly exposed 25 micron square down to the substrate wherein thethickness of the photoresist after development depends on the local doseof UV irradiation. The exposure time or intensity is adjusted to takeinto account the non-linear photo-response of the particular photoresist and proximity effects. Similar modulation of the mask pattern canbe utilized to create varying compositional changes with respect tocompositional change materials. In a specific embodiment, exposure timeand/or light intensity can be varied as a function of position on thesubstrate to effect compositional changes with respect to compositionalchange materials of the substrate.

In an embodiment, the gray scale controller can use a pulse widthmodulation scheme to modulate the mask pattern provided to themicromirror array 14. By applying pulse width modulation to the controlmask pattern information, the micromirrors of the array 14, drivenreflect light to the photosensitive material according to the maskpattern, are further directed to occasionally reflect light awayaccording to the duty cycle of the pulse code modulation. For example,in a pulse code modulation scheme, the duty cycle for the angulardeflection could be adjusted so that a desired feature is exposed (bydirecting the mirrors to reflect light to the feature on thephotosensitive material) for 90% of the total exposure time and masked(by directing the mirrors to reflect light away from the feature on thephotosensitive material) the remaining 10% of the total exposure time.With respect to a feature exposed for 100% of the exposure time, thefeature exposed for only 90% of the entire exposure time will beproportionately smaller because of the decreased exposure time and theresulting curing response of the photoreactive material.

In addition to time modulation of the mask pattern, the pattern can alsobe spatially modulated to provide continuously variable patternexposure. In spatial modulation, the varying thicknesses and/orcomposition of photoreactive material can be sculpted by modulating thepositioning of the mirrors in the micromirror array that are alreadypositioned to form a mask pattern. In this embodiment, the mirrors aredirected to different areas of the substrate, and the desired areaexposed sequentially in a series of directly radiating exposures.Consequently, gray scaling is accomplished by applying fewer sequentialexposure steps to the desired area to create thinner thickness ofphotoreactive material, and applying a greater number of sequentialexposure steps to the desired area to create thicker thickness and/orcompositional changes of photoreactive material. As a resultcontinuously variable thicknesses can be created by selectivelycontrolling the number of sequential exposure steps.

In yet another embodiment, spatial modulation can be combined with timemodulation to create continuously variable thickness and/or composition.Both the number of sequential exposure steps and the modulation of themirror positioning during each exposure step provides further controlover the gray scaling process.

In still another embodiment, a plasma display device 13 is used as botha light source and pattern generator. In this embodiment the intensityof each pixel of light is variably excited and/or modulated to creategray scaled patterns. In addition, spatial modulation can be employed asdescribed above, and both intensity modulation and spatial modulationcan be combined to create gray scale patterns on substrates.

In addition to providing gray scale patterns, by dynamically modulatingthe mirrors as described, the mirrors can be dynamically positioned soas to reduce stiction of the mirrors. Further, pixelation effects on thesubstrate are reduced by providing mask pattern coverage of theinterpixel areas not exposed to direct, on axis illumination.

If further exposures are desired in step 72, such as required whencreating three-dimensional objects, the above method is repeated byreturning to step 52 until the desired object is fabricated. A newdigital mask pattern is provided, another photoreactive coat is applied,and the substrate is realigned and re-exposed. Once the desired objecthas been created, the process ends in step 74.

III. Large Area Patterning Maskless Photolithography

Referring now to FIGS 1A and 1B, embodiments of the current inventionfor creating large area patterns on substrates will be described. In thelarge area patterning embodiments, a maskless photolithography system isprovided that enables efficient writing of patterns to large areas inorder to permit maximal image resolution for a maximal field size. Apatterned light generator projects images onto photo reactive compoundsmounted on a movable alignment fixture 22. In a specific embodiment, thesystem uses a micromirror array device as described previously and shownin FIG 1A, to direct patterned light to a substrate 20. In an alternateembodiment, the system uses a plasma display device as describedpreviously and shown in FIG. 1B, to generate and direct patterned lightto a substrate 20. During exposure, the patterned light generator movesacross a large substrate 20, while at the same time successivelychanging the projected pattern to a large image exposure area.Alternatively, the substrate 20 is moved under the patterned light beam27 while at the same time the projected pattern is successively changedto expose a large area. In yet another embodiment, the computer system16 can control the movement of the substrate under the patterned lightbeam 27 to synchronize the patterned light projected on the substratewith the desired substrate area of projection.

Turning now to FIG. 4, a method of using the current invention tophotoform large area photosensitive materials using masklessphotolithography will now be described. It should be understood that incertain situations for reasons of computational efficiency or ease ofmaintenance, the ordering and relationships of the blocks of theillustrated flow charts could be rearranged or re-associated by oneskilled in the art. Starting from step 80, a photosensitive material isprovided for exposure to the patterned light beam 27 in step 82. Forexample, the substrate 20 is affixed to alignment fixture 22 and coatedwith a layer of photoreactive chemicals 21 for exposure to the patternedlight beam 27. Next, a desired mask pattern is designed and stored oncomputer system 16 in step 84. Alternatively, mask patterns can bedesigned on other computer systems and imported into computer system 16.After the mask pattern is provided for exposure, the filter 11 is placedin the light beam 26 path according to step 86 to filter the light andprevent exposure of the photosensitive material until the system hasbeen aligned.

Next, the computer system 16 is instructed to provide the resident maskpattern information to the pattern generator in step 88, and the patterngenerator responds by providing a patterned light beam 27 to thephotosensitive material according to the desired pattern in step 90.With the desired pattern projected on the photosensitive material, thematerial can be manually aligned in three dimensions according to step92, for example, by moving alignment fixture 22 to ensure that thephotosensitive material is properly located in light beam 26. Properalignment is verified by viewing the projected pattern on thephotosensitive material through optical viewer 24. In an optionalembodiment, once the photosensitive material is manually aligned,alignment information can be provided to computer system 16 and computersystem 16 automatically adjusts the pattern generator by shifting thepattern in two dimensions to attain proper alignment in step 94. Havingaligned the photosensitive material, the filter is removed from lightbeam 26 in step 96 and the photosensitive material is exposed in step98, allowing the light to cause a photoreaction in the photosensitivematerial for a required reaction time depending on the photoreactivechemicals used.

For large area patterning, steps 84 through 98 are repeated until thedesired large area has been exposed. Specifically, if another area ofthe photosensitive material needs to be exposed in step 100, the systemcan be realigned to expose that area 104. Such realignment can beperformed manually and/or automatically. For example, the patterngenerator is moved to illuminate a new area on the photosensitivematerial or the photosensitive material is moved under the light beam toexpose a new area. In an embodiment, the relative movement of thepattern generator and the photosensitive material is synchronized tomutually align the pattern generator and the photosensitive materialwith respect to each other to expose new areas. Movement is provided intwo coplanar dimensions perpendicular to the incident patterned lightbeam 27. Alternatively, movement is provided in a linear one-dimensionaldirection, such as in a conveyor belt fashion.

After the alignment to expose a new area of the photosensitive material104, the mask pattern is shifted 106 to provide the appropriate patternfor the new area to be exposed and the process returns to step 84. Theprocess described in steps 84 through 98 is then repeated. If no otherareas need to be exposed, the process ends on step 102. Following thedescribed procedure, large area patterns can be created, includinggeneration of large 3 dimensional patterns by sequentially exposinglayers on top of previously created layers.

The system and method can be used to produce large areamicroelectronics, large area micro-electromechanical systems, large areaprinted materials, large area sensors, whole wafer patterning, mixedscale electronics (printed wiring boards and micro-electromechanicalsystems), mixed signal electronic patterning (digital circuitry andanalog circuitry, large area printed inks (graphic and electronic) andsystems on a wafer. The subject invention can also be used to producelarge area variable 2D and 3D materials of any composition that may bephoto imageable, or may be non-photo imageable materials defined byphoto imageable material/features.

IV. Method for Maskless Photolithography

A method of using the current invention to fabricate designs will now bedescribed. It should be understood that in certain situations forreasons of computational efficiency or ease of maintenance, the orderingand relationships of the blocks of the illustrated flow charts could berearranged or re-associated by one skilled in the art. Referring to FIG.5, starting from step 50, a desired mask pattern is designed and storedon computer system 16 in step 52. Alternatively, mask pattern designscan be designed on other computer systems and imported into computersystem 16. Next, in step 54, a substrate 20 is placed on alignmentfixture 22 and coated with a layer of photoreactive chemicals 21 in step56. Once the substrate is mounted in alignment fixture 22, the filter 11is placed in the light beam 26 path according to step 58 to filter thelight and prevent exposure of the substrate. Next, the computer system16 can then be instructed to provide the resident mask patterninformation to micromirror array 14 as shown in step 60, and themicromirror array 14 responds by orienting each individual mirror toreflect or direct light beam 26 away from substrate 20 according to thedesired pattern. Next, alignment of the substrate is enabled by excitingthe light source 10 to provide a light beam in step 62, projecting lightbeam 26 through first lens system 12, and then onto micromirror array14. In turn, micromirror array 14 reflects light beam 26 through secondlens system 18 and onto layer of photoreactive chemicals 21 andsubstrate 20.

With the desired pattern projected on substrate 20, alignment fixture 22can be manually aligned in three dimensions according to step 64 bymoving alignment fixture 22 to ensure that substrate 20 is properlylocated in light beam 26. Proper alignment can be verified by viewingthe projected pattern on substrate 20 through optical viewer 24. Oncesubstrate 20 is manually aligned, alignment information can optionallybe provided to computer system 16 and computer system 16 automaticallyadjusts the micromirror 14 by shifting the pattern in two dimensions toattain proper alignment in optional step 66. Having aligned substrate20, the layer of photoreactive chemicals 21 on substrate 20 is exposedin step 70 by removing filter 11 from light beam 26 in step 68 andallowing the light to cause a reaction between layer of photoreactivechemicals 21 and substrate 20 for a required reaction time depending onthe photoreactive chemicals used. For example, using standard Novolac™positive photoresist, an exposure time of 60 seconds is used. In anembodiment, during exposure step 70, the angular position and timeduration of the angular positioning of the mirrors in micromirror array14 is varied according to commands from computer system 16. For example,when masking a 25 micron square feature, angular position and timeduration of the angular positioning of the mirrors in micromirror array14 might be varied so that the mask effectively covers an area of 36microns square, centered on the desired 25 micron square feature. As afurther example, the duty cycle for the angular deflection could beadjusted so that the 25 micron square feature is masked 90% of the totalexposure time and the remaining 11 square micron area is covered 10% ofthe total exposure time. By dynamically modulating the mirrors asdescribed, stiction of the mirrors is reduced. Further, pixelationeffects on the substrate are reduced by providing mask pattern coverageof the interpixel areas not exposed to direct, on axis illumination.

In an embodiment in which alignment 22 is interconnected with computersystem 16, the movement and/or rotation of the substrate can be effectedvia instructions sent to the alignment fixture 22 from computer system16 in accordance with the desired mask pattern. Accordingly, multipleexposures of the substrate can be accomplished for each coating of thesubstrate, for example with the substrate in different positions and/orrotations, so as to accomplish the desired mask pattern.

If further exposures are desired in step 72, such as required whencreating three-dimensional objects, the above method is repeated byreturning to step 52 until the desired object is fabricated. A newdigital mask pattern is provided, another photoreactive coat is applied,and the substrate is realigned and re-exposed. Once the desired objecthas been created, the process ends in step 74.

V. Exemplary Embodiment

An example of the current invention using the system and methoddescribed above will now be presented. In an embodiment, the currentinvention is designed to be an integrated, reconfigurable, rapidprototyping maskless photography system. The system provides optics, alight source, and integrated electronic components used to directlygenerate patterns for the exposure of photoresist and otherphotoimagable materials. A broad band spectrum, high intensity whitelight source provides the exposure energy for the process. This light isthen filtered and optimized for the exposure process, using a variety ofintegrated optical components. A direct coupled optical delivery systemensures efficient transfer of the light energy. Using proven opticaltechniques, the projected image is free of distortion and uniformthrough out the exposure area. With the optimized optical stream, theimage is imposed in the light path, providing the final exposurepattern. This pattern is then transferred to the substrate surface andused to expose the photosensitive material required in the user'sfabrication process.

A personal computer operably connected to a micromirror array to providemask patterns. The mask patterns are generated in the computer and thentransferred to the micromirror array to provide the optical pattern forexposure. The pattern is transferred to a substrate and is observedusing an optical microscope. This microscope is needed for patternalignment to the substrate. Alignment is controlled through the use of acourse alignment stage provided by a mechanically movable substratemounting alignment fixture, combined with a fine, electronic alignmentstage. This fine alignment stage is computer controlled and aligns themask pattern reflected from the micromirror instead of moving thealignment fixture, thereby offering exceptional accuracy andrepeatability. Once alignment is complete, substrate exposure occurs.Through the use of a step and repeat method, the entire substratesurface can be exposed and multiple layers can be created using analignment stage movable in a direction parallel to the light beam.

In the exemplary embodiment, the light source exhibits a spectral peakat 436 nm as shown in FIG. 6. As a result the invention produces lightcompatible with g-line photoresist material and other photopolymers thatactivate in this spectral region. In addition, typical exposure energydensity for a 2.5 cm by 2.5 cm exposure area is 225 mj/cm². However, theenergy density can be adjusted as required. By using DMDs designed towithstand higher levels and different wavelengths of UV light, differentfrequencies can be used, such as UV light having a spectral peak at 365nm.

FIG. 7 shows how the minimum feature size varies depending on thedesired exposure area. The invention is capable of creating features assmall as 5 micrometers (μm) for an exposure area of 6.25 millimeters(mm) by 6.25 mm. As shown on the graph, as the desired minimum featuresize increases, the exposure feature size increases linearly. Forexample, for a minimum feature size of 20 μm, the exposure field isincreased to 25 mm by 25 mm.

In addition, according the invention, three-dimensional patterns can becreated using the three dimension alignment capabilities disclosedabove. For example, patterning using thick photo resist or multiplayerpatterning of individual photoresist layers. These techniques can be useto provide either a photomask for subsequent etching of substratematerials or if the photopolymer is compatible with the chemistry usedin the device, the fabricated features can be used as part of the deviceitself.

Based on the foregoing specification, the computer system of thedisclosed invention may be implemented using computer programming orengineering techniques including computer software, firmware, hardwareor any combination or subset thereof. Any such resulting program, havingcomputer-readable code means, may be embodied or provided within one ormore computer-readable media, thereby making a computer program product,i.e., an article of manufacture, according to the invention. Thecomputer readable media may be, for instance, a fixed (hard) drive,diskette, optical disk, magnetic tape, semiconductor memory such asread-only memory (ROM), etc., or any transmitting/receiving medium suchas the Internet or other communication network or link. The article ofmanufacture containing the computer code may be made and/or used byexecuting the code directly from one medium, by copying the code fromone medium to another medium, or by transmitting the code over anetwork.

One skilled in the art of computer science will easily be able tocombine the software created as described with appropriate generalpurpose or special purpose computer hardware to create a computer systemor computer sub-system embodying the method of the invention. Anapparatus for making, using or selling the invention may be one or moreprocessing systems including, but not limited to, a central processingunit (CPU), memory, storage devices, communication links and devices,servers, I/O devices, or any sub-components of one or more processingsystems, including software, firmware, hardware or any combination orsubset thereof, which embody the invention. User input may be receivedfrom the keyboard, mouse, pen, voice, touch screen, or any other meansby which a human can input data into a computer, including through otherprograms such as application programs.

It should be understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication.

1. A maskless photolithography system for large area photoforming ofphotosensitive materials comprising: a. a computer system for generatingmask patterns and alignment instructions; b. a maskless patterned lightgenerator, operably connected to said computer system, for receivingsaid mask patterns and alignment instructions, radiating a patternedlight beam directed at the photosensitive material, wherein saidpatterned light beam is generated in conjunction with said alignmentinstructions; and c. a movable mount to provide relative movement ofsaid maskless patterned light generator and the photosensitive materialexposed to said patterned light, wherein the pattern of said patternedlight beam is generated in conjunction with the relative movement ofsaid maskless patterned light generator and the photosensitive materialto provide large area photoforming of the photosensitive material. 2.The system of claim 1, wherein said relative movement is provided bymounting said maskless photolithography system on said movable mount andmoving said mount in relation to the photosensitive material.
 3. Thesystem of claim 1, wherein said relative movement is provided bymounting the photosensitive material on said movable mount and movingsaid mount in relation to said maskless photolithography system.
 4. Thesystem according to claim 1, wherein the moveable mount is automaticallycontrolled.
 5. The system of claim 1, wherein said maskless patternedlight generator comprises: a. an array of positionable micromirrors,wherein said micromirrors reflect light according to said mask patternsprovided by said computer system; b. an optical system for generating,collimating, and directing the light beam to said micromirror array; andc. an optical system for further collimating the light beam reflectedfrom said mirrors and directing said patterned light beam onto thephotosensitive material and to create patterns on the photosensitivematerial corresponding to said mask patterns.
 6. The system of claim 1,wherein said maskless patterned light generator comprises a plasmadisplay having individually addressable pixels, operably connected toand controllable by said computer system, wherein said display generatessaid patterned light beam corresponding to said mask patterns providedby said computer system to expose the photosensitive material to saidpatterned light beam and to create patterns on the photosensitivematerial corresponding to said mask patterns.
 7. The system of claim 1,wherein said maskless patterned light generator comprises a liquidcrystal display having individually addressable pixels, operablyconnected to and controllable by said computer system, wherein saidpixels are addressed to transmit or block light corresponding to saidmask patterns provided by said computer system to provide a patternedlight beam to expose the photosensitive material and create patterns onthe photosensitive material corresponding to said mask patterns.
 8. Thesystem of claim 1, wherein said movable mount is a manually controlledalignment mount, wherein said alignment mount is movable in coplanarfirst and second dimensions, and in a third dimension directionsubstantially perpendicular to said first and second coplanar dimensionsand substantially parallel to said patterned light beam; said mountproviding three dimensional alignment, wherein said alignment mount ismoved in three dimensions in response to mechanical alignments directlyprovided by a user.
 9. The system of claim 1, wherein the movable mountis an automatically controlled alignment mount, wherein the alignmentmount is movable in coplanar first and second dimensions, and in a thirddimension direction substantially perpendicular to the first and secondcoplanar dimensions and substantially parallel to the patterned lightbeam; the mount providing three dimensional alignment, wherein thealignment mount is moved in three dimensions in response to alignmentsinstruction provided by the computer system.
 10. The system of claim 1,further comprising a computer controlled pattern alignment system, forproviding electrical alignment of said patterns in coplanar first andsecond dimensions, wherein said pattern alignment system adjusts thealignment of said mask patterns in coplanar first and second dimensionsin response to instructions provided by said computer according to saidalignment information, so that said pattern is shifted in at least onecoplanar direction.
 11. The system of claim 1, further comprising anoptical viewer to allow optical monitoring of positioning of theimmersed substrate mounted in said alignment fixture by visuallyverifying that an image projected on the immersed substrate is properlyaligned.
 12. The system of claim 11, wherein the optical viewercomprises a device selected from the group consisting of: a camera, avision system, and a microscope.
 13. The system of claim 1, furthercomprising an optical filter, removably mounted in the light beam toselectively filter light impinging on the immersed substrate to preventexposure of the immersed substrate during an alignment procedure.
 14. Amaskless photolithography method for large area photoforming ofphotosensitive materials comprising: a. receiving mask patterninformation and alignment information corresponding to a desired patternto be created on the photosensitive material; b. generating maskpatterns based on received mask pattern information and alignmentinformation; c. providing said mask patterns to a patterned lightgenerator; d. generating a patterned light beam; e. directing saidpatterned light beam onto a first exposure area of the photosensitivematerial; f. exposing the first exposure area of the photosensitivematerial to said gray scale patterned light beam; g. providing relativemovement of the photosensitive material and the masklessphotolithography system to allow exposure of a second exposure area; andh. repeating steps a-g to sequentially expose the entire surface of thephotosensitive material; wherein said patterned light beam incident onthe photosensitive material photosculpts the photosensitive material tocreate contiguous patterns by sequential exposure corresponding to saidpatterned light beam.
 15. The method of claim 14, wherein generatingsaid patterned light beam further comprises: a. receiving said maskpatterns at an array of positionable micromirrors; b. generating,collimating, and directing a light beam to said micromirror array; c.positioning said micromirrors to reflect the light beam from saidmicromirror array according to said mask patterns; and d. collimatingsaid patterned light beam reflected from said micromirror array.
 16. Themethod of claim 14, wherein generating said patterned light beam furthercomprises: a. receiving mask patterns at a plasma display, havingindividually addressable pixels, operably connected to and controllableby said computer system, b. activating the pixels of said plasma displayto generate a patterned light beam corresponding to said mask patternsprovided by said computer system; and c. collimating said patternedlight beam generated by said plasma display.
 17. The method of claim 14,further comprising: a. providing selective filtering of said patternedlight beam impinging on the photosensitive material to prevent exposureof an area of the photosensitive material during an alignment procedure;b. allowing manual alignment of the photosensitive material under saidpatterned light beam by moving said mounted photosensitive material inthree dimensions, wherein the photosensitive material is moved incoplanar first and second dimensions, and moved in a third dimensiondirection substantially perpendicular to said first and second coplanardimensions, and substantially parallel to the patterned light beam; c.allowing optical monitoring of positioning of an area of thephotosensitive material under the gray scale patterned light beam tovisually verify that an image projected on the photosensitive materialis properly aligned; d. receiving alignment information corresponding toalignment of a desired mask pattern projected onto an area of thephotosensitive material; e. generating alignment instructions based onreceived said alignment information; f. providing alignmentinstructions, based on said alignment information, to said patternedlight generator to further align said gray scale mask patterns in thecoplanar first and second dimensions; g. adjusting said micromirrorarray according to said alignment instructions by shifting the maskpattern in at least one of the coplanar first and second dimensions; h.disabling filtering of said gray scale patterned light beam; i. exposingthe photosensitive material; and j. repeating steps (a-i) to create adesired pattern on the photosensitive material.
 18. The method of claim17, wherein allowing optical monitoring of positioning of an area of thephotosensitive material is accomplished via an optical viewer comprisinga device selected from the group consisting of: a camera, a visionsystem, and a microscope.
 19. A computer system for large scale,maskless photolithography comprising: a. a computing device comprising adisplay, a central processing unit (CPU), operating system software,memory for storing data, a user interface, and input/output capabilityfor reading and writing data; said computing device operably connectedto and operating in conjunction with a maskless patterned lightgenerator; b. computer program code for: 1) receiving mask patterninformation and alignment information corresponding to a desired patternto be created on a photosensive method; 2) generating mask patternsbased on received mask pattern information and alignment information;and 3) providing said mask patterns to a maskless pattern generator;whereby said computing device operates in conjunction with said masklessphotolithography system and executes said computer code to sequentiallyprovide mask patterns to said maskless pattern generator.
 20. Thecomputer system according to claim 19, wherein the computing devicecomprises a means for connecting to and interoperating with a networkfor sharing digital design data.